1. Field of the Invention
The present invention relates to a method for manufacturing a wiring substrate, a thin film transistor, a display device and a television device.
2. Description of the Related Art
A thin film transistor (hereinafter referred to as a “TFT”) and an electric circuit using the thin film transistor are formed by laminating various kinds of thin films containing semiconductor, insulator or conductor over a substrate and adequately patterning into predetermined shapes using photolithography. Photolithography is a technique in which a pattern of a circuit or the like, which is referred to as a photomask and formed using a material that does not transmit light, over a transparent flat plate is transferred to an intended substrate by utilizing light. The photolithography technique is widely used in a process of manufacturing a semiconductor integrated circuit and the like.
The conventional manufacturing process using photolithography requires multiple steps such as exposure, development, baking and peeling only for treating a mask pattern formed by using a photosensitive organic resin material that is referred to as a photoresist. Therefore, the manufacturing cost is inevitably increased with increasing the number of photolithography steps. In order to solve this problem, it has been attempted to manufacture TFTs with lower number of photolithography steps (e.g., see the patent document 1).    [Patent Document 1]: Japanese Patent Application Laid-Open No. Hei 11-251259